Absorbent cores having channel-forming areas and c-wrap seals

ABSTRACT

Substantially planar absorbent core comprising at least 80% and up to 100% by weight of superabsorbent polymer as absorbent material on an absorbent material deposition area and a core wrap. The absorbent material deposition area comprises at least one absorbent material-free channel-forming areas through which the top and bottom substrates of the core wrap are bonded together. An auxiliary glue is applied directly at least to the inner surface of the first substrate on an auxiliary glue application area. The auxiliary glue application area is smaller than the absorbent material deposition area and the core comprises at least one C-wrap seal along at least one edge, in particular along the two longitudinally extending edges of the core.

FIELD OF THE INVENTION

The invention relates to absorbent cores and their use in absorbentarticles such as, but not limited to, baby diapers, training pants,feminine pads or adult incontinence products.

BACKGROUND OF THE INVENTION

Absorbent articles for personal hygiene of the type indicated above aredesigned to absorb and contain body exudates, in particular largequantity of urine. These absorbent articles comprise several layersproviding different functions, for example a topsheet, a backsheet andin-between an absorbent core, among other layers. The function of theabsorbent core is typically to absorb and retain the exudates for aprolonged amount of time, minimize re-wet to keep the wearer dry andavoid soiling of clothes or bed sheets.

The majority of currently marketed absorbent articles comprise asabsorbent material a blend of comminuted wood pulp with superabsorbentpolymers (SAP) in particulate form, also called absorbent gellingmaterials (AGM), see for example U.S. Pat. No. 5,151,092 (Buell).Absorbent articles having a core consisting essentially of SAP asabsorbent material (so called “airfelt-free” cores) have also beenproposed (see e.g. U.S. Pat. No. 6,790,798 (Suzuki), WO2008/155699(Hundorf), WO95/11652 (Tanzer), WO2012/052172 (Van Malderen)). Absorbentcores with slits or grooves have also been proposed, typically toincrease the fluid acquisition properties of the core or to act as afolding guide.

The immobilization of the SAP within the core, in both wet and drystate, can be a particular challenge for absorbent articles havingairfelt-free cores. U.S. Pat. No. 6,790,798 (Suzuki) and WO 2008/155699(Hundorf) disclose absorbent cores with a patterned layer of SAPimmobilized by depositing a layer of fibrous thermoplastic adhesivematerial over the layer of SAP. The fibrous thermoplastic material helpsto maintain the position of the SAP in the absorbent core prior to andduring use of the article, without substantially restricting the abilityof the SAP to absorb large volumes of urine.

WO2012/170778 (Rosati et al., see also WO2012/170779, WO2012/170781 andWO2012/170808) discloses absorbent structures that comprisesuperabsorbent polymers, optionally a cellulosic material, and at leasta pair of substantially longitudinally extending channels. The core wrapcan be adhesively bonded through the channels to form a channel bond.The channel bonds may be permanent, so that their integrity is at leastpartially maintained both in dry and wet state. As the absorbentstructure absorbs liquid and swells, the absorbent structure takes athree-dimensional shape with the channels becoming visible. The channelsare indicated to provide improved fit and/or better liquidacquisition/transportation, and/or improved performance throughout theuse of the absorbent structure. In some preferred embodiments, the coreincludes a first adhesive material applied to the absorbent layer,preferably said first adhesive material being a thermoplastic fibrousadhesive material, and a second adhesive material may be present betweenthe supporting sheet and the absorbent layer.

While the absorbent cores of the prior art generally have goodproperties, there is a continuous need to reduce the usage of rawmaterial, in particular adhesive material, while improving or at leastmaintaining key properties such as SAP immobilization and fluidacquisition.

SUMMARY OF THE INVENTION

The invention is as indicated in the claims. In particular, in a firstaspect the invention is for a substantially planar absorbent coreextending in a transversal direction and a longitudinal direction, theabsorbent core having a front edge, a back edge and two longitudinallyextending side edges. The absorbent core comprises a core wrap having afirst substrate and a second substrate wherein each substrate comprisesan inner surface and an outer surface, an absorbent material comprisingat least 80% and up to 100% by weight of superabsorbent polymer, anddefining an absorbent material deposition area between the firstsubstrate and the second substrate. The absorbent material depositionarea encompasses one or more area(s) substantially free of absorbentmaterial. An auxiliary glue is applied directly to the inner surface ofthe first substrate on an auxiliary glue application area. The auxiliaryglue at least partially bonds the inner surface of the first substrateto the inner surface of the second substrate through at least one ormore of the area(s) substantially free of absorbent material, so thatwhen the absorbent material swells the core wrap forms channels in thebonded areas substantially free of absorbent material. The auxiliaryglue application area is smaller than the absorbent material depositionarea. One of the first substrate or the second substrate comprises atleast one outwardly extending flap which is folded around at least oneof the front, back or any of the side edges and the extending flap(s)is/are bonded to the external surface of the other substrate to form atleast one C-wrap seal. The absorbent core may comprise in particular twoflaps each laterally extending over a side edge to form twolongitudinally extending side C-wrap seals.

The present inventors have found that the proposed invention can solvethe problems mentioned in the preamble section. The C-wrap seals of theinvention can cooperate with the core wrap bonds provided within theabsorbent material deposition area to reduce the freedom of movement ofthe SAP particles. The amount and area covered by the auxiliary glue canbe reduced relative to previous known executions while keepingsatisfactory immobilization of the SAP.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an absorbent core according to the inventionwith some of the layers partially removed;

FIG. 2 is a transversal cross-section of the core of FIG. 1;

FIG. 3 is a longitudinal cross-section of the core showing an optionaldual layer construction for the absorbent layer;

FIG. 4 is a close-up view of a section of FIG. 3;

FIG. 5 is an exploded view of the upper absorbent structure forming halfof the absorbent core shown in FIG. 3, wherein the auxiliary glue isshown applied as a series of slots on an application area, the slotsbeing shorter than the absorbent material deposition area in thelongitudinal direction;

FIG. 6 is a top view of an alternative absorbent core wherein theauxiliary glue is applied on an area shorter in the longitudinal andtransversal direction than the absorbent material deposition area;

FIG. 7 is a top view of an alternative absorbent core wherein theauxiliary glue is applied on two sub-areas;

FIG. 8 is a top view of an exemplary diaper comprising an absorbent coreof the invention;

FIG. 9 shows a transversal cross-section of FIG. 8;

FIG. 10 shows a transversal cross-section as in FIG. 9 when theabsorbent core has swollen after absorbing a fluid;

FIG. 11 shows schematically an apparatus for making an absorbent coreaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION Introduction

As used herein, the terms “comprise(s)” and “comprising” are open-ended;each specifies the presence of the feature that follows, e.g. acomponent, but does not preclude the presence of other features, e.g.elements, steps, components known in the art or disclosed herein. Theseterms based on the verb “comprise” should be read as encompassing thenarrower terms “consisting essentially of” which excludes any element,step or ingredient not mentioned which materially affect the way thefeature performs its function, and the term “consisting of” whichexcludes any element, step, or ingredient not specified. Any preferredor exemplary embodiments described below are not limiting the scope ofthe claims, unless specifically indicated to do so. The words“typically”, “normally”, “preferably”, “advantageously”, “in particular”and the likes also qualify features which are not intended to limit thescope of the claims unless specifically indicated to do so.

Unless indicated otherwise, the description and claims refer to theabsorbent core and article before use (i.e. dry, and not loaded with afluid) and conditioned at least 24 hours at 21° C.+/−2° C. and 50+/−20%Relative Humidity (RH).

General Description of the Absorbent Core 28

As used herein, the term “absorbent core” refers to an individualcomponent, which is placed, or is intended to be placed, within anabsorbent article and which comprises an absorbent material enclosed ina core wrap. As used herein, the term “absorbent core” does not includethe topsheet, the backsheet and (if present) an acquisition-distributionlayer or multilayer system, which is not integral part of the absorbentcore, in particular which is not placed within the core wrap. Theabsorbent core is typically the component of an absorbent article thathas the most absorbent capacity of all the components of the absorbentarticle and which comprises all, or at least the majority of,superabsorbent polymer (SAP). The core may consist essentially of, orconsist of, the core wrap, the absorbent material and adhesives. Theterms “absorbent core” and “core” are herein used interchangeably.

The absorbent cores of the invention are substantially planar. Bysubstantially planar, it is meant that the absorbent core can be laidflat on a surface. The absorbent core may also be typically thin andconformable, so that it can also be laid on a non-flat surface forexample a drum during its making process or stored as a continuous rollof stock material before being converted into an absorbent article. Forease of discussion, the exemplarily absorbent core of FIG. 1 isrepresented in a flat state and extending in a transversal direction (x)and a longitudinal direction (y). Unless otherwise indicated, dimensionsand areas disclosed herein apply to the core in this flat-outconfiguration. The same applies to the absorbent article, as exemplarilyrepresented in FIG. 8, in which the core is integrated. For ease ofdiscussion, the absorbent cores and articles of the invention will bediscussed with reference to the Figures and the numerals referred to inthese Figures; however these are not intended to limit the scope of theclaims unless specifically indicated.

The absorbent core comprises a front edge 280, a back edge 282 and twolongitudinally extending side edges 284, 286 joining the front edge andthe back edge. The front edge of the core is the edge of the coreintended to be placed towards the front edge of the absorbent article inwhich the core is or will be integrated. Typically the absorbentmaterial 60 of the core may be advantageously distributed in somewhathigher amount towards the front edge than towards the back edge as moreabsorbency is typically required towards the front half of the article.Typically the front and back edges 280, 282 of the core may be shorterthan the side edges 284, 286 of the core. The absorbent core may alsocomprise a top side 288 and a bottom side 290. The top side of the coreis the side placed or intended to be placed towards the topsheet 24 ofthe article and the bottom side is the side placed or intended to beplaced towards the backsheet 25 in the finished article. The top side ofthe core wrap is typically more hydrophilic than the bottom side.

The absorbent core may be notionally (i.e. virtually) divided by alongitudinal axis 80 extending from the front edge to the back edge anddividing the core in two substantially symmetrical halves relative tothis axis, when viewing the core in the plane formed by the longitudinaland transversal direction (x, y). The absorbent core can typically begenerally rectangular with a width W in the transversal direction and alength L in the longitudinal direction as measured from edge to edge,including the region of the core wrap which does not enclose theabsorbent material, in particular at the front and back end seals whenpresent. In case the core is not rectangular, the maximum dimensionmeasured along the transversal and longitudinal direction can be used toreport the length and width of the core. The width and length of thecore may vary depending on the intended usage. For baby and infantdiapers, the width L may for example in the range from 40 mm to 200 mmand the length from 100 mm to 500 mm.

The transversal axis 90 of the core (herein also referred to as “crotchline”), is the virtual line perpendicular to the longitudinal axis andpassing through the crotch point C of the core. The crotch point C isdefined as the point of the absorbent core placed at a distance of 0.45of L from the front edge of the absorbent core, L being the length ofthe core as measured from the front edge 280 in direction of the backedge 282, as shown on FIG. 1. The crotch region of the core is definedherein as the region of the core extending from the crotch line, i.e. atthe level of the crotch point C, towards the back edge and front edge ofthe core by a distance of a quarter of L (L/4) in both directions for atotal length of L/2. The front region and back region of the core arethe remaining regions of the core towards the front and back edges ofthe core respectively.

The core wrap comprises a first substrate and a second substrate 16, 16′which, as will be described in more details below, form at least oneC-wrap seal 284′, 286′ along at least one edge of the core, inparticular one C-wrap seal along each of the longitudinally extendingside edges of the core. The absorbent material comprises a highproportion of superabsorbent polymer (herein abbreviated as “SAP”)enclosed within the core wrap. The SAP content represents at least 80%and up to 100% by weight of the absorbent material contained in the corewrap. The SAP may in particular be in particulate forms (SAP particles).The core wrap is not considered as absorbent material for the purpose ofcalculating the percentage of SAP in the absorbent core.

The absorbent material comprises at least 80%, optionally at least 90%and up to 100%, by weight of superabsorbent polymer material. Theabsorbent material may be in particular free of cellulose fibers. Theabsorbent core may thus be relatively thin, in particular thinner thanconventional cores comprising cellulosic fibers. In particular, thecaliper of the core (before use) as measured at the crotch point (C) orat any other points of the surface of the core according to the CoreCaliper Test as described herein may be from 0.25 mm to 5.0 mm, inparticular from 0.5 mm to 4.0 mm.

The absorbent material 60 defines an absorbent material deposition area73 as seen from above within the plane of the core. The absorbent corecomprises one or more areas 26 free of absorbent material, which areencompassed within the absorbent material deposition area, and throughwhich the first substrate and the second substrate are bonded to eachother. As will detailed below, the bond 27 between the substrates inthese area is at least partially formed by an auxiliary glue 72 applieddirectly to the inner surface of at least one of the substrate on anauxiliary glue application area 71. This bonding allows the materialfree zones 26 to form channels 26′ as the absorbent material swells whenit absorbs a liquid such as urine. The absorbent material depositionarea 73 may be formed by one or in some embodiments two absorbent layersapplied on the substrate in pattern of land areas 75 separated byjunction areas 76, as exemplary shown for the absorbent structure 70 onFIG. 5. In particular, two absorbent layers having offset land andjunction areas may be combined to form an absorbent material depositionarea in which the absorbent material is substantially continuous, asshown in FIG. 3. The absorbent core may advantageously further comprisea fibrous thermoplastic adhesive 74 to further immobilize the absorbentmaterial and/or help forming the bond within the material free zones ofthe absorbent core.

The surface of the auxiliary glue application area 71 is according tothe invention smaller than the surface of the absorbent materialdeposition area 73, but is at least partially present in the absorbentmaterial free zone 26, so that the auxiliary glue 72 may at leastpartially form the bond between the inner surfaces of the substrates.The size of the auxiliary glue application area 71 may be tailoredaccording to the distribution of the absorbent material desired. Forexample, for cores having an overall relatively low amount of SAP, it ispossible to reduce the auxiliary glue application area substantially tothe zones corresponding to the absorbent material free zone(s) 26. Onthe other hand, the auxiliary glue application area 71 may also extendto zones not directly adjacent to the channel-forming zones 26 a, 26 bbut where relatively high amount of SAP are deposited, as will typicallybe present in the crotch region and the front region of the core, tocontribute to their immobilization. Having a smaller auxiliary glueapplication area 71 provides the advantages of reducing the overallamount of glue used while keeping the function of the glue where it ismost needed. Combining the auxiliary glue layer with a C-wrap seal alongat least one and preferably two edges of the core, and optionally afurther fibrous adhesive web 74, provides a sufficient immobilization ofthe absorbent material in dry and wet state. The absorbent coreadvantageously achieve an SAP loss of no more than about 70%, 60%, 50%,40%, 30%, 20%, or 10% according to the Wet Immobilization Test describedin US2010/0051166A1.

The absorbent cores of the invention will typically be used in anabsorbent article, for example a taped diaper as shown on FIG. 8 in aflat-out state. The longitudinal axis 80 of the core may be thencontiguous with the longitudinal axis 80′ of the article. The articlemay further comprise a liquid permeable topsheet 24; a liquidimpermeable backsheet 25 with the absorbent core 28 positioned betweenthe topsheet and the backsheet.

The absorbent cores and articles of the invention will be furthergenerally described below and by way of illustration with theembodiments exemplarily shown in the Figures, which are not consideredlimiting the scope of the invention unless indicated otherwise.

Substrates 16, 16′

The core wrap is defined by the first substrate 16 and second substrates16′ and encloses the absorbent material. The first and second substratesmay be part from a single web of material folded around the absorbentmaterial as in a parcel wrap. However, the first substrate and secondsubstrate are advantageously comprised of two separate webs of materialwhich are attached to each other along the edges of the absorbent core.The substrates may be formed by any materials suitable for receiving andcontaining the absorbent material. Typical substrate materials used inthe production of conventional cores may be used, in particular paper,tissues, films, wovens or nonwovens, or laminate of any of these. Thecore wrap may in particular be formed by a nonwoven web, such as acarded nonwoven, spunbond nonwoven (“S”) or meltblown nonwoven (“M”),and laminates of any of these. For example spunmelt polypropylenenonwovens are suitable, in particular those having a laminate web SMS,or SMMS, or SSMMS, structure, and having a basis weight range of about 5gsm to 15 gsm. Suitable materials are for example disclosed in U.S. Pat.No. 7,744,576, US 2011/0268932 A1, US 2011/0319848 A1 and US2011/0250413 A1. Nonwoven materials provided from synthetic fibers maybe used, such as PE, PET and in particular PP.

As used herein, the terms “nonwoven layer” or “nonwoven web” generallymeans a manufactured sheet, web or batt of directionally or randomlyorientated fibers, bonded by friction, and/or cohesion and/or adhesion,excluding paper and products which are woven, knitted, tufted,stitch-bonded incorporating binding yarns or filaments, or felted bywet-milling, whether or not additionally needled. The fibers may be ofnatural or synthetic origin and may be staple or continuous filaments orbe formed in situ. Commercially available fibers have diameters rangingfrom less than about 0.001 mm to more than about 0.2 mm and they come inseveral different forms such as short fibers (known as staple, orchopped), continuous single fibers (filaments or monofilaments),untwisted bundles of continuous filaments (tow), and twisted bundles ofcontinuous filaments (yam). Nonwoven webs can be formed by manyprocesses such as meltblowing, spunbonding, solvent spinning,electrospinning, carding and airlaying. The basis weight of nonwovenwebs is usually expressed in grams per square meter (g/m² or gsm).

As represented in the Figures, the first substrate 16 may substantiallyform the whole of the top surface 288 of the core wrap and the secondsubstrate 16′ substantially the whole of the bottom surface 290 of thecore wrap, but it is not excluded that this may be the other way round.By “substantially forming the whole of the surface” it is meant that theoutwardly extending flaps of the other substrate may also form part ofthe surface considered. The substrates are typically substantiallyplanar in the same plane as the absorbent core, and each comprises anexternal surface and an internal surface. The internal surface isorientated towards the absorbent material and the external surface isthe opposite surface. At least one of the substrate comprises at leastone, and advantageously two outwardly extending flaps, which are foldedaround the front, back or side edges of the absorbent core and thenattached to the external surface of the other substrate to form at leastone so-called C-wrap seal. This is exemplarily represented in FIG. 2,where the first substrate comprises two side flaps laterally extendingalong the length of the core and which are folded over each side edge284, 286 of the absorbent core. The flaps may be attached to the outersurface of the second substrate for example by using an adhesive seal284′, 286′ along each C-wrap seal. One or two continuous orsemi-continuous lines of glue may be typically applied along the lengthof the flaps to bond the inner surface of the flaps to the externalsurface of the other substrate.

As exemplarily represented in FIG. 3, the core may also compriseso-called sandwich seals 280′, 282′ where the two substrates are bondedalong one edge of the core to each other in face-to-face relationshipwith the inner surface of each substrate bonded to the inner surface ofthe other substrate. These sandwich seals can for example be formedusing a hotmelt glue applied in a series of stripes in a directionperpendicular of the edge, as shown on the front edge 280 and back edge282 of the core on FIG. 1 for example,

The substrates may typically be commercially supplied as rolls ofmaterial of several hundred meters of length. Each roll is thenintegrated in the converting line and unrolled at high speed while theauxiliary adhesive, the absorbent material and the fibrous thermoplasticadhesive layer if present are deposited or applied on the substrate andthen further converted into an absorbent core when a core wrap enclosingthe absorbent material is formed by the second substrate. Typically themachine direction (MD) of the converting line may correspond to thelongitudinal direction (y) of the substrate/core and the cross-machinedirection (CD) to the transversal direction (x) of the substrate/core.The substrates may be cut along the front and back edges of the core280, 282 to individualize the core. This will be further exemplarilydiscussed in the process section further below.

The inner surface of first substrate is at least partially bonded to theinner surface of the second substrate by the auxiliary glue through oneor more area(s) 26 a,b substantially free of absorbent materialencompassed in the absorbent material deposition area 73. The auxiliaryglue may be applied directly on the first substrate and/or the secondsubstrate. It is also not excluded that the bond between the twosubstrates may be reinforced by the fibrous glue layer 74 if present, orusing additional bonding solution such as thermo and/or pressure bondingthe two substrates in the material free areas 26. A second auxiliaryglue layer may also be present on the other substrate. When theabsorbent material swells upon absorption of a liquid such as urine, thecore wrap gradually forms channels 26′ along these bonded areas 26 a,b.

The channel-forming absorbent material-free areas 26 a,b may belongitudinally-extending but the areas need not extend solely in thelongitudinal direction; they may for example be arcuate or oblique tothe longitudinal direction. The channels may provide the article withgreater lateral flexibility during use of the article as well asimproved fluid distribution along the channels.

Absorbent Material 60

The absorbent material comprises a relative high amount ofsuperabsorbent polymer (herein referred to as “SAP”). The SAP useful inthe present invention includes a variety of water-insoluble, butwater-swellable polymers capable of absorbing large quantities offluids. The absorbent material comprises at least 80%, in particular atleast 85%, 90%, 95% and up to 100%, of superabsorbent polymer by weightof the absorbent material. The absorbent material may in particularcomprise no or only small amount of cellulose fibers, such as less than20%, in particular less than 10%, 5% or even 0% of cellulose fibers byweight of the absorbent material. The absorbent material may thusadvantageously consist or consist essentially of SAP. The SAP may betypically in particulate forms (superabsorbent polymer particles), butit not excluded that other form of SAP may be used such as asuperabsorbent polymer foam for example.

The term “superabsorbent polymer” refers herein to absorbent materials,which may be crosslinked polymeric materials, that can typically absorbat least 10 times their weight of an aqueous 0.9% saline solution asmeasured using the Centrifuge Retention Capacity (CRC) test (EDANAmethod WSP 241.2-05E). The SAP may in particular have a CRC value ofmore than 20 g/g, or more than 24 g/g, or of from 20 to 50 g/g, or from20 to 40 g/g, or 24 to 30 g/g.

The superabsorbent polymers may be in particulate form so as to beflowable in the dry state and thus easily deposited on the substrate.Typical particulate absorbent polymer materials are made ofpoly(meth)acrylic acid polymers. However, starch-based particulateabsorbent polymer materials may also be used, as well polyacrylamidecopolymer, ethylene maleic anhydride copolymer, crosslinkedcarboxymethylcellulose, polyvinyl alcohol copolymers, crosslinkedpolyethylene oxide, and starch grafted copolymer of polyacrylonitrile.The superabsorbent polymer may be polyacrylates and polyacrylic acidpolymers that are internally and/or surface crosslinked. Suitablematerials are described in WO 07/047598, WO 07/046052, WO 2009/155265and WO 2009/155264. In some embodiments, suitable superabsorbent polymerparticles may be obtained by current state of the art productionprocesses as is more particularly as described in WO 2006/083584. Thesuperabsorbent polymers are preferably internally crosslinked, i.e. thepolymerization is carried out in the presence of compounds having two ormore polymerizable groups which can be free-radically copolymerized intothe polymer network. In some embodiments, the SAP are formed frompolyacrylic acid polymers/polyacrylate polymers, for example having aneutralization degree of from 60% to 90%, or about 75%, having forexample sodium counter ions.

The SAP particles may be relatively small (under 1 mm in their longestdimension) in their dry state and may be roughly circular in shape, butgranules, fibers, flakes, spheres, powders, platelets and other shapesand forms are also known to persons skilled in the art. Typically, theSAP may be in the form of spherical-like particles. In contrast tofibers, “spherical-like particles” have a longest and a smallestdimension with a particulate ratio of longest to smallest particledimension in the range of 1-5, where a value of 1 would equate aperfectly spherical particle and 5 would allow for some deviation fromsuch a spherical particle. The superabsorbent polymer particles may havea particle size of less than 850 μm, or from 50 to 850 μm, preferablyfrom 100 to 710 μm, more preferably from 150 to 650 μm, as measuredaccording to EDANA method WSP 220.2-05. SAP having a relatively lowparticle size help to increase the surface area of the absorbentmaterial which is in contact with liquid exudates and therefore supportfast absorption of liquid exudates.

The absorbent core will typically comprise only one type of SAP, but itis not excluded that a blend of SAPs may be used. The fluid permeabilityof a superabsorbent polymer can be quantified using its UrinePermeability Measurement (UPM) value, as measured in the test disclosedEuropean patent application number EP 12174117.7. The UPM of the SAP mayfor example be of at least 10×10⁻⁷ cm³·sec/g, or at least 30×10⁻⁷cm³·sec/g, or at least 50×10⁻⁷ cm³·sec/g, or more, e.g. at least 80 or100×10⁻⁷ cm³·sec/g. The flow characteristics can also be adjusted byvarying the quantity and distribution of the SAP used in the secondabsorbent layer.

Absorbent Material Deposition Area 73

The absorbent material 60 enclosed within the core wrap has an absorbentmaterial deposition area 73, as seen in the plane of the absorbent core.The absorbent material deposition area 73 is defined by the periphery ofthe layer formed by the absorbent material 60 within the core wrap, asseen from the top side of the absorbent core as shown on FIG. 1, andcomprises the absorbent material free areas 26 a,b encompassed within.The absorbent material deposition area 73 can be generally rectangular,for example as shown in FIG. 1, but other shapes can also be used suchas a “T” or “Y” or “sand-hour” or “dog-bone” shape. In particular thedeposition area may show a tapering along its width at the crotch regionof the core. In this way, the absorbent material deposition area mayhave a relatively narrow width in an area of the core intended to beplaced in the crotch region of the absorbent article. This may providefor example better wearing comfort. The absorbent material depositionarea 73 may for example have a width (as measured in the transversaldirection x) at its narrowest point which is less than about 100 mm, 90mm, 80 mm, 70 mm, 60 mm or even less than about 50 mm. This narrowestwidth may be for example at least 5 mm, or at least 10 mm, smaller thanthe width of the deposition area at its largest point in the frontand/or back regions of the deposition area 73.

Without considering the absorbent material free areas 26 a,b, the basisweight (amount deposited per unit of surface) of the SAP may also bevaried along the deposition area 73 to create a profiled distribution ofabsorbent material, in particular SAP, in the longitudinal direction y(as schematically shown in FIG. 3), in the transversal direction (x), orboth directions of the core. Hence along the longitudinal axis 80 of thecore, the basis weight of absorbent material may vary, as well as alongthe transversal axis, or any axis parallel to any of these axes. Thebasis weight of SAP in area of relatively high basis weight may thus befor example at least 10%, or 20%, or 30%, or 40%, or 50% higher than inan area of relatively low basis weight. In particular the SAP present inthe absorbent material deposition area at the longitudinal position ofthe crotch point C may have more SAP per unit of surface deposited ascompared to at least one other area of the absorbent material depositionarea 73, in particular in the crotch region of the core.

The absorbent material 60 may be deposited on any of the substratesusing known techniques, which may allow relatively precise deposition ofSAP at relatively high speed. In particular the SAP printing technologyas disclosed for example in US2006/024433 (Blessing), US2008/0312617 andUS2010/0051166A1 (both to Hundorf et al.) may be used. This techniqueuses a transfer device such as a printing roll to deposit SAP onto asubstrate disposed on a grid of a support which may include a pluralityof cross bars extending substantially parallel to and spaced from oneanother. The areas 26 substantially free of absorbent material can beformed for example by modifying the pattern of the grid and receivingdrums so that no SAP is applied in the selected areas, as exemplarydisclosed in US2012/0312491 (Jackels). This technology allows high-speedand precise deposition of SAP on a substrate in particular to provideone or more area(s) 26 substantially free of absorbent materialsurrounded by absorbent material.

The absorbent material may be substantially continuously distributed inthe deposition area 73. By “substantially continuous” it is meant thatat least 50%, or at least to 70% and up to 100% of the deposition areacomprises a continuous layer of absorbent material as seen from the topside of the core. The absorbent material may be for example applied as asingle continuous layer on one of the substrate, the layer thus directlyforming the material deposition area 73.

A continuous layer of absorbent material, in particular of SAP, may alsobe obtained by combining two absorbent layers having matchingdiscontinuous absorbent material application pattern wherein theresulting layer is substantially continuously distributed across theabsorbent material deposition area 73, as exemplarily taught inUS2008/0312622A1 (Hundorf), and as exemplarily shown on FIG. 3-4. A suchindividual absorbent layer 61 is shown in isolation and exploded view onFIG. 5. Each absorbent material layer 61, 62 comprises a pattern havingabsorbent material land areas 75, 75′ separated by absorbentmaterial-free junction areas 76, 76′. The absorbent material areas 75 ofthe first layer correspond substantially to the absorbent material-freejunction areas 76′ of the second layer and vice versa. As exemplaryshown in FIGS. 3-4, the absorbent core 28 may thus comprise a firstabsorbent layer 61 and a second absorbent layer 62 depositedrespectively on the first substrate 16 and second substrate 16′ andcombined together.

FIG. 5 shows in more details the first substrate 16, a layer ofauxiliary glue 72 as will described hereafter applied by slot coating ina series of slots 72 s, a first layer of absorbent material 61 in apattern having laterally orientated absorbent material land areas 75separated by absorbent material-free junction areas 76, and an optionalbut preferred at least one fibrous glue layer 74 covering the absorbentmaterial land areas 75 and absorbent material-free junction areas 76 tofurther immobilize the absorbent material layer 61 on the firstsubstrate. The absorbent material layer also comprises absorbentmaterial free areas 26 a, 26 b through which the substrate 16 will beattached to the second substrate 16′. The first and second absorbentlayers 61,62 may be deposited as transversal stripes or “land areas”having the same width as the desired absorbent material deposition area73 on their respective substrate before being combined. Each absorbentlayer 61 may comprise for example between 5 and 50 of these generallyrectangular land areas. These land areas may have for example a widthranging from 4 to 20 mm, in particular 10 mm, as measured in thelongitudinal direction (y). The land areas 75 may be of uniform lengthin the transversal direction (x) but they may have different width, inparticular towards the center or crotch section of the absorbentstructure to form so called “dog bone” or “hour-glass” shape, whichshows a tapering along its width at least in the crotch zone of thestructure.

The width of the junction areas 76 between the land areas 75 maytypically be shorter than the width of the land areas, for examplehaving a width exemplarily ranging from 0.5 to 6 mm, for example 1 to 2mm. Of course other patterns of deposition for the absorbent materialare possible, for example the absorbent material may be deposited as anarray of circular or ovoid land areas, or combination of rectangularland areas with circular or ovoid land areas.

In many applications, the liquid discharge occurs predominantly in onearea of the core. For diapers, the liquid may predominantly be releasedtowards the crotch region of the core and to a lesser extent the frontof the core. Relatively less liquid may be released towards the back ofthe core. Thus it may be beneficial to profile the amount of absorbentmaterial along the longitudinal direction of the absorbent structure sothat more absorbent material is present in the areas where the liquid ismore likely to insult the core. The land areas 75 may advantageouslycomprise varying amount of absorbent material to provide a profiledbasis weight along the longitudinal and/or transversal direction of thecore.

As indicated above, the junction areas 76 of an absorbent layer 61 mayadvantageously be not directly recognizable in the absorbent core asthey will be filled with the land area 75′ of the opposed absorbentlayer 62, as shown on FIG. 4. On the other hand, it is an object of theinvention that the absorbent material deposition area 73 encompasses atleast one, in particular two, areas 26 free of absorbent materialthrough which the substrates are bonded to another.

Area(s) 26 Substantially Free of Absorbent Material and Channels 26′

The absorbent material deposition area 73 of the core encompasses one ormore area(s) 26 which is/are substantially free of absorbent material.By “substantially free” it is meant that in each of these areas thebasis weight of the absorbent material is at least less than 25%, inparticular less than 20%, less than 10%, of the average basis weight ofthe absorbent material in the rest of the absorbent material depositionarea 73 of the core. In particular there can be no absorbent material inthese areas 26 ab. Minimal amount such as involuntary contaminationswith absorbent material particles that may occur during the makingprocess are not considered as absorbent material. The areas 26 areadvantageously surrounded by the absorbent material, when consideringthe plane of the core, which means that the area(s) 26 does not extendto any of the edges of the deposition area 73 of the absorbent material.

The top side 16 of the core wrap is attached to the bottom side 16′ ofthe core wrap by at least one core wrap bond(s) 27 through these area(s)26 substantially free of absorbent material. As illustrated in FIG. 10,when the absorbent material 60 swells upon absorbing a liquid, the corewrap bond(s) 27 remain(s) at least initially attached in thesubstantially material free area(s) 26. The absorbent material 60 swellsin the rest of the core when it absorbs a liquid, so that the core wrapforms one or more channel(s) 26′ along the area(s) 26 substantially freeof absorbent material comprising the core wrap bond 27. These channels26′ are three dimensional and can serve to distribute an insulting fluidalong their length to a wider area of the core. They may provide aquicker fluid acquisition speed and a better utilization of theabsorbent capacity of the core. The channels 26′ can also provide adeformation of an overlying layer such as a fibrous layer 54 and providecorresponding ditches 29 in the overlying layer. It is not excluded thatthe absorbent core may comprise other area(s) substantially free ofabsorbent material but without a core wrap bond, but these non-bondedareas will typically not form a channel when wet.

The inner surface of the first substrate 16 and the inner surface of thesecond substrate 16′ may be attached together continuously along thearea(s) 26 substantially free of absorbent material, but the core wrapbond 27 may also be discontinuous (intermittent) such as formed byseries of point bonds. The auxiliary glue at least partially helpsforming the substrates bond 27. Typically, some pressure may be appliedon the substrates in the areas 26 so that the auxiliary glue may betterattach to and form the bonds between the substrates. If an optionalfibrous adhesive 74, 74′ is present, it may also help forming the bond27, and it also possible to additionally form the bond via other knownattachment means, such as pressure bonding, ultrasonic bonding or heatbonding or combination thereof. If the auxiliary glue is applied as aseries of continuous slots 72 s, the width and frequency of these slotsmay advantageously be such that at least one slot of auxiliary glue ispresent at any level of the channel in the longitudinal direction. Forexample the slots may be 1 mm wide with a 1 mm distance between eachslots, and the channel-forming area(s) have a width of about 8 mm. Suchon average for 4 slots of auxiliary glue will be present in area(s) 26.

The following examples of the shape and size of the channel-formingareas 26 substantially free of absorbent material are not limiting. Ingeneral, the core wrap bond 27 may have the same outline but be slightlysmaller than the areas 26 due to the tolerance required in somemanufacturing process. The substantially absorbent material free area(s)26 may be present within the crotch region of the core, in particular atleast at the same longitudinal level as the crotch point C, asrepresented in FIG. 1 by the two longitudinally extending areassubstantially free of absorbent material 26 a, 26 b. The absorbent core28 may also comprise more than two substantially absorbent material freearea(s), for example at least 3, or at least 4 or at least 5 or at least6. The absorbent core may comprise one or more pairs of areas 26 a, 26 bsubstantially free of absorbent material symmetrically arranged relativeto the longitudinal axis 80. Shorter area(s) substantially free ofabsorbent material may also be present, for example in the back regionor the front region of the core, as seen for example in the Figures ofWO2012/170778.

The channel-forming area(s) 26 may extend substantially longitudinally,which means typically that each area extends at least as much in thelongitudinal direction (y) than in the transversal direction (x), andtypically at least twice as much in the longitudinal direction than inthe transverse direction (as measured after projection on the respectiveaxis). The area(s) 26 substantially free of absorbent material may havea length L′ projected on the longitudinal axis 80 of the core that is atleast 10% of the length L of the absorbent core, in particular from 20%to 80%. It may be advantageous that at least some or all of thechannel-forming area(s) 26 are not completely or substantiallycompletely transversely oriented. The area(s) substantially free ofabsorbent material may have a width Wc along at least part of its lengthwhich is at least 2 mm, or at least 3 mm or at least 4 mm, up to forexample 20 mm, or 16 mm or 12 mm. The width Wc of the area(s)substantially free of absorbent material may be constant throughsubstantially its whole length or may vary along its length.

The area(s) 26 substantially free of absorbent material may becompletely oriented longitudinally and parallel to the longitudinal axisbut also may be curved. In particular some or all these area(s), inparticular these area(s) present in the crotch region, may be concavetowards the longitudinal axis 80, as for example represented in FIG. 1for the pair of channels 26 a,b. The radius of curvature may typicallybe at least equal (and preferably at least 1.5 or at least 2.0 timesthis average transverse dimension) to the average transverse dimensionof the absorbent material deposition area 73; and also straight butunder an angle of (e.g. from 5°) up to 30°, or for example up to 20°, orup to 10° with a line parallel to the longitudinal axis. The radius ofcurvature may be constant for a substantially absorbent material freearea(s), or may vary along its length. This may also includes area(s)substantially free of absorbent material with an angle therein, providedsaid angle between two parts of a channel is at least 120°, preferablyat least 150°; and in any of these cases, provided the longitudinalextension of the area is more than the transverse extension. Thesearea(s) may also be branched, for example a central substantiallymaterial free area superposed with the longitudinal axis in the crotchregion which branches towards the back and/or towards the front of thearticle.

In some embodiments, there is no area(s) substantially free of absorbentmaterial that coincides with the longitudinal axis 80 of the core. Whenpresent as one or more symmetrical pair(s) relative to the longitudinalaxis, the area(s) substantially free of absorbent material may be spacedapart from one another over their whole longitudinal dimension. Thesmallest spacing distance may be for example at least 5 mm, or at least10 mm, or at least 16 mm.

Furthermore, in order to reduce the risk of fluid leakages, the area(s)substantially free of absorbent material may advantageously not extendup to any of the edges of the absorbent material deposition area 73, andare therefore surrounded by and fully encompassed within the absorbentmaterial deposition area 73 of the core. Typically, the smallestdistance between an area(s) substantially free of absorbent material andthe closest edge of the absorbent material deposition area is at least 5mm.

The channels 26′ in the absorbent core start forming when the absorbentmaterial absorbs a liquid such as urine and starts swelling. As the coreabsorbs more liquid, the depressions within the absorbent core formed bycore wrap bond 27 between the two substrates will become deeper and moreapparent to the eye and the touch. It is possible to create asufficiently strong core wrap bond combined with a relatively low amountof SAP and/or a relatively extensible substrate material so that thechannels remain permanent until complete saturation of the absorbentmaterial. On the other hand, the core wrap bonds may in some cases alsorestrict the swelling of the absorbent material when the core issubstantially loaded. The core wrap bond 27 may also be designed togradually open in a controlled manner when exposed to a large amount offluid. The bonds may thus remain substantially intact at least during afirst phase as the absorbent material absorbs a moderate quantity offluid, as shown on FIG. 10. In a second phase the core wrap bonds 27 inthe channels can start opening to provide more space for the absorbentmaterial to swell while keeping most of the benefits of the channelssuch as increased flexibility of the core in transversal direction andfluid management. In a third phase, corresponding to a very highsaturation of the absorbent core, a more substantial part of the channelbonds can open to provide even more space for the swelling absorbentmaterial to expand. The strength of core wrap bond 27 within thechannels can be controlled for example by varying the amount and natureof the glue used for the attaching the two sides of the core wrap, thepressure used to make the core wrap bond and/or the distribution of theabsorbent material, as more absorbent material will usually causes moreswelling and will put more pressure on the bond. The extensibility ofthe material of the core wrap may also play a role.

Auxiliary Glue 72 and Auxiliary Application Glue Area 71

An auxiliary glue 72 is applied directly over the substrate 16 on anauxiliary glue application area 71. The auxiliary glue at leastpartially form the bonds 27 between the inner surface of the firstsubstrate 16 and the inner surface of the second substrate 16′ throughthe area(s) 26 a,b substantially free of absorbent material. Theauxiliary glue 72 may also be useful to improve the adhesion between thefirst substrate 16 and both the absorbent material (in the absorbentmaterial land areas 75) and the fibrous thermoplastic material 74 (inthe absorbent material-free junction areas 76).

The auxiliary glue 72 may comprise or consist of any kind ofthermoplastic hot-melt adhesives used in the field of absorbent coremaking Such an adhesive generally includes one or more polymers toprovide cohesive strength (e.g., aliphatic polyolefins such asethylene-propylene copolymers, polyetheramides, polyetheresters, andcombinations thereof; ethylene vinyl acetate copolymers;styrene-butadiene or styrene-isoprene block copolymers; etc.), a resinor analogous material (sometimes called a tackifier) to provide adhesivestrength (e.g., hydrocarbons distilled from petroleum distillates;rosins and/or rosin esters; terpenes derived, for example, from wood orcitrus, etc.); and optional waxes, plasticizers or other materials tomodify viscosity (e.g., mineral oil, polybutene, paraffin oils, esteroils, and the like), and/or other additives including, but not limitedto, antioxidants or other stabilizers. Exemplary suitable commercialadhesives are available from Fuller under reference number 1286 or 1358.Further information about hotmelt adhesive chemistry is discussed belowfibrous thermoplastic adhesive layer 74.

The auxiliary glue 72 can be applied by any adhesive applicator known inthe field, in particular bead, slot or spray nozzles. The auxiliary gluemay be in principle applied as a continuous film on the whole of theauxiliary glue application area 71, however this may unduly increase theusage of adhesive material. Typically the adhesive will thus be applieddiscontinuously to maximize the area covered with a lower amount ofadhesive. The auxiliary glue may thus be applied as a relatively widecurtain of adhesive using as a spray nozzle. The auxiliary glue may alsobe applied discontinuously as a series of discrete application zoneswithin the application area. For example, the auxiliary glue can beapplied using a slot coating process as a pattern comprising a pluralityof spaced-apart slots which may each extend in the longitudinaldirection, as represented in FIG. 5 by the slots 72 s. The slots may forexample have a width of from 0.5 mm to 3 mm, and/or have a lateralspacing there-between of from 0.5 mm to 4 mm. The slots 72 s may all beof equal length as represented in FIG. 5, but may also have varyinglength. For example if the absorbent material was also profiledlaterally with more material towards the center of the substrate it maybe beneficial to have longer or wider slots towards the center of thesubstrate. In the example of FIG. 5, the absorbent material is notprofiled in the transversal direction. The auxiliary adhesive materialslots 72 s in this example are regularly spaced and all have the samelength and width. Each slot may be applied continuously in thelongitudinal direction as represented in FIG. 5 but they may also beapplied discontinuously. The slots may all have the same length or mayhave different lengths, in case more SAP immobilization was requested insome areas. When applied as slots, the auxiliary glue 72 in the slots 72s may for example be applied at a basis weight in the range from 1 gsmto 20 gsm, in particular from 2 gsm to 10 gsm, for example 3 or 4 gsm.More generally, considering the auxiliary glue application 71 as awhole, with any areas free of glue between the slots or any areas freeof glue within for example the lines of a spiral glue application, thebasis weight over the whole application area may for example be half thebasis weight indicated above for the slots 72 s. The basis weight mayalso vary locally within the auxiliary glue application area 71.

The “auxiliary glue application area” as used herein means the smallestarea 71 in the plane of the substrate 16 whose periphery encompasses theauxiliary glue 72 and any areas free of auxiliary glue between theauxiliary glue. The auxiliary glue application area 71 is smaller thanthe absorbent material deposition area 73. The auxiliary glue may thusbe advantageously be applied in the area of the first substrate 16 whereit is most needed, foremost where the channel-forming region(s) 26 a,bare present and a bond 27 between the two substrates is desired, andtypically at or close to the crotch region of the absorbent core as wellwhere the amount of absorbent material may be typically higher than inthe back region of the core. Reducing the auxiliary glue applicationarea 71 relative to the absorbent material deposition area 73 has theadvantage that typically less auxiliary glue material is used comparedto a full application area. Reducing the amount and area of theauxiliary glue may also provide improved fluid acquisition properties ashotmelt glue are typically hydrophobic as well as reduced undesired gluesmell in the finished product.

In general, the auxiliary glue application area may be at least 20%smaller than the absorbent material deposition area 73, in particularfrom 20% to 80% smaller than the absorbent material deposition area 73.The areas are compared by measuring their surface in the plane of theabsorbent core and including the channel-forming area 26′ in theabsorbent material deposition area 73.

The auxiliary glue application area may be shorter in the longitudinaldirection (y) and/or in the transversal direction (x) than the absorbentmaterial deposition area 73. The auxiliary glue application area 71 maybe for example generally rectangular and have about the same width asthe absorbent material deposition area 73 while being shorter in thelongitudinal direction (y). FIG. 1 shows such an example where theauxiliary glue application area 71 and absorbent material depositionarea 73 are both rectangular, have the about the same width and whereinthe application area 71 is longitudinally shorter than the depositionarea 73 and does not extend to any of the front or back ends of theabsorbent material deposition area. FIG. 6 illustrates an alternativeconfiguration where the auxiliary glue application area 71 is shorter inboth longitudinal and transversal directions than the absorbent materialdeposition area 73. Of course many different configurations for the bothareas are possible, as the absorbent material deposition area 73 mayalso be shaped instead of rectangular. The auxiliary glue applicationarea 71 may also for example extend from the front end of the absorbentmaterial deposition area 73 and along its width and stop before the backend of the absorbent material deposition area. This may be advantageousfor application having a relatively high amount of AGM towards the frontof the core, where the auxiliary glue may be needed there. The auxiliaryglue application area may also have a shape which is not rectangular butfor example having a central body with two adjoined side wings which areshorter than the central body. The wings may or may not extend to thelateral edges of the absorbent material deposition area but they mayalso extend to these edges if desired. These sections of differentlengths may for example be easily obtained using a slot coating processand tuning the slot nozzles to apply the hot-melt adhesive on a shorterdistance on the sides of the application area compared to the center ofthe application area.

The auxiliary glue application area 71 may have any shape adapted to theintended usage of the absorbent article and the distribution ofabsorbent material. In particular, the auxiliary glue application areamay be rectangular, shaped with a tapering in the central region of thesubstrate, or with a central elongated portion and shorter sideportions. It is also possible that the auxiliary glue application areacomprises separated sub-areas 71 a, 71 b, as illustrated on FIG. 7. Asub-area is hereby defined as an adhesive application area separatedfrom another at least about 10 mm. In that case the adhesive free areabetween the adhesive application sub-areas is not considered to be partof the auxiliary glue application area, for example for thedetermination of the surface of the auxiliary glue area 71. Such aconfiguration is illustrated on FIG. 7 where the auxiliary glueapplication area 71 consists of two sub-zones 71 a and 71 b, each ofthese zones generally corresponding to one channel-forming area 26 a, 26b and separated by a distance of about 10 mm.

In the above description, the auxiliary glue 72 was discussed withreference to the first absorbent substrate 16 which forms the upper side288 of the absorbent core, and which is placed towards the topsheet 24in the finished absorbent article 20. This is however not limiting, asthe first substrate may alternatively form the bottom side 290 of theabsorbent core which is placed towards the backsheet 25 of the article20. It is also considered that a second auxiliary glue may be applieddirectly on the second substrate in addition to the first auxiliary glueapplied directly on the first substrate, in particular in any of theconfigurations discussed above. This may be particular useful when theabsorbent material within the core wrap comprises two layers 61, 62 asdiscussed above.

Microfiber glue 74, 74′

The absorbent core 28 may also comprise a fibrous thermoplastic adhesivematerial 74, to further immobilize the absorbent material 60 during themaking process of the core and usage of the article. The fibrousthermoplastic adhesive material 74, 74′ may be in particular useful toimmobilize the layer of absorbent materials 61, 62 to their respectivesubstrate 16, 16′. These absorbent layer(s) may comprise land areas 75,75′ separated by junction areas 76, 76′ as discussed above and thefibrous thermoplastic adhesive material 74 may then be at leastpartially in contact with the absorbent material 61, 62 in the landareas and at least partially in contact with the substrate layer 16, 16′in the junction areas. This imparts an essentially three-dimensionalnet-like structure to the fibrous layer of thermoplastic adhesivematerial, which in itself is essentially a two-dimensional structure ofrelatively small thickness, as compared to the dimension in length andwidth directions. Thereby, the fibrous thermoplastic adhesive materialmay provide cavities to cover the absorbent material in the land areas,and thereby immobilizes this absorbent material. The fibrous adhesivemay be for example sprayed on an absorbent layer after it has beendeposited on its substrate during the core making process.

The fibrous thermoplastic adhesive material may typically have amolecular weight (Mw) of more than 10,000 and a glass transitiontemperature (Tg) usually below room temperature or −6° C.<Tg<16° C.Typical concentrations of the polymer in a hotmelt are in the range ofabout 20% to about 40% by weight. The thermoplastic polymers may bewater insensitive. Exemplary polymers are (styrenic) block copolymersincluding A-B-A triblock structures, A-B diblock structures and (A-B)nradial block copolymer structures wherein the A blocks arenon-elastomeric polymer blocks, typically comprising polystyrene, andthe B blocks are unsaturated conjugated diene or (partly) hydrogenatedversions of such. The B block is typically isoprene, butadiene,ethylene/butylene (hydrogenated butadiene), ethylene/propylene(hydrogenated isoprene), and mixtures thereof. Other suitablethermoplastic polymers that may be employed are metallocene polyolefins,which are ethylene polymers prepared using single-site or metallocenecatalysts. Therein, at least one comonomer can be polymerized withethylene to make a copolymer, terpolymer or higher order polymer. Alsoapplicable are amorphous polyolefins or amorphous polyalphaolefins(APAO) which are homopolymers, copolymers or terpolymers of C2 to C8alpha olefins.

The tackifying resin may exemplarily have a Mw below 5,000 and a Tgusually above room temperature, typical concentrations of the resin in ahotmelt are in the range of about 30 to about 60%, and the plasticizerhas a low Mw of typically less than 1,000 and a Tg below roomtemperature, with a typical concentration of about 0 to about 15%.

The thermoplastic adhesive used for the fibrous layer preferably haselastomeric properties, such that the web formed by the fibers on theSAP layer is able to be stretched as the SAP swell. Exemplaryelastomeric, hotmelt adhesives include thermoplastic elastomers such asethylene vinyl acetates, polyurethanes, polyolefin blends of a hardcomponent (generally a crystalline polyolefin such as polypropylene orpolyethylene) and a Soft component (such as ethylene-propylene rubber);copolyesters such as poly(ethylene terephthalate-co-ethylene azelate);and thermoplastic elastomeric block copolymers having thermoplastic endblocks and rubbery mid blocks designated as A-B-A block copolymers:mixtures of structurally different homopolymers or copolymers, e.g., amixture of polyethylene or polystyrene with an A-B-A block copolymer;mixtures of a thermoplastic elastomer and a low molecular weight resinmodifier, e.g., a mixture of a styrene-isoprenestyrene block copolymerwith polystyrene; and the elastomeric, hot-melt, pressure-sensitiveadhesives described herein. Elastomeric, hot-melt adhesives of thesetypes are described in more detail in U.S. Pat. No. 4,731,066 (Korpman).

The thermoplastic adhesive material fibers may exemplarily have anaverage thickness of about 1 to about 50 micrometers or about 1 to about35 micrometers and an average length of about 5 mm to about 50 mm orabout 5 mm to about 30 mm. The auxiliary glue may improve the adhesionof the thermoplastic adhesive material to the substrate. The fibersadhere to each other to form a fibrous layer, which can also bedescribed as a mesh.

General Description of the Absorbent Article 20

An exemplary absorbent article 20 according to the invention in the formof a baby taped diaper 20 is represented in FIGS. 8 and 9. FIG. 8 is atop plan view of the exemplary diaper 20, in a flat-out state, withportions of the structure being cut-away to more clearly show theconstruction of the diaper 20. FIG. 9 is transversal cross-sectionalview of the diaper 20 taken along line 9-9 in FIG. 8. This diaper 20 isshown for illustration purpose only as the invention may be used formaking a wide variety of diapers or other absorbent articles.

The absorbent article 20 comprises a liquid permeable topsheet 24, aliquid impermeable backsheet 25 and an absorbent core 28 according tothe invention between the topsheet 24 and the backsheet 25. Theabsorbent article may also comprise further typical components such asan acquisition layer and/or a distribution layer (collectively referredto as acquisition-distribution system “ADS”, designated as 54), andelasticized gasketing cuffs 32 present between topsheet and backsheetand upstanding barrier leg cuffs 34, which will be further detailed inthe following. The Figures also show other typical taped diapercomponents such as a fastening system comprising fastening tabs 42attached towards the back edge 12 of the article and cooperating with alanding zone 44 towards the front edge 10 of the article. The absorbentarticle may also comprise other typical components, which are notrepresented in the Figures, such as a back elastic waist feature, afront elastic waist feature, transverse barrier cuffs, a lotionapplication, etc.

The absorbent article 20 comprises a front edge 10, a back edge 12, andtwo longitudinally extending side (lateral) edges 13, 14. The front edge10 is the edge of the article which is intended to be placed towards thefront of the user when worn, and the back edge 12 is the opposite edge.The absorbent article may be notionally divided by a longitudinal axis80′ extending from the front edge to the back edge of the article anddividing the article in two substantially symmetrical halves relative tothis axis, when viewing the article from the wearer facing side in aflat out configuration, as exemplarily shown in FIG. 8. This axis 80′may typically be concomitant with the longitudinal axis 80 of the core.If some part of the article is under tension due to elasticizedcomponents, the article may be typically flattened using clamps alongthe periphery of the article and/or a sticky surface, so that thetopsheet and backsheet can be pulled taut so as to be substantiallyflat. Closed articles such as training pant may be cut open along theside seams to apply them on a flat surface. Unless otherwise indicated,dimensions and areas disclosed herein apply to the article in thisflat-out configuration. The article has a length L″ as measured alongthe axis 80′ from the back edge to the front edge. The absorbent article20 can also be notionally divided by a transversal axis 90′ into a frontregion and a back region of equal length measured on the longitudinalaxis, when the article is in such a flat state. This article'stransversal axis 90′ is perpendicular to the longitudinal axis 80′ andplaced at half the length of the article.

The topsheet 24, the backsheet 25, the absorbent core 28 and the otherarticle components may be assembled in a variety of well-knownconfigurations, in particular by gluing and/or heat embossing. Exemplarydiaper assemblies are for example generally described in U.S. Pat. No.3,860,003, U.S. Pat. No. 5,221,274, U.S. Pat. No. 5,554,145, U.S. Pat.No. 5,569,234, U.S. Pat. No. 5,580,411, and U.S. Pat. No. 6,004,306. Theabsorbent article is preferably thin. The article may be advantageouslythin at the intersection of the longitudinal and transversal axes, forexample with a caliper of from 1.0 mm to 8.0 mm, in particular from 1.5mm to 6.0 mm, as measured using the Absorbent Article Caliper Testdescribed below.

These and other components of the article will now be discussed in moredetail. Dimensions and values disclosed herein are not to be understoodas being strictly limited to the exact numerical values recited.Instead, unless otherwise specified, each such dimension is intended tomean both the recited value and a functionally equivalent rangesurrounding that value. For example, a dimension disclosed as “40 mm” isintended to mean “about 40 mm”.

Topsheet 24

The topsheet 24 is the part of the absorbent article 20 that is directlyin contact with the wearer's skin. The topsheet 24 can be joined to thebacksheet 25, the absorbent core 28 and/or any other layers as is knownin the art (as used herein, the term “joined” encompasses configurationswhereby an element is directly secured to another element by affixingthe element directly to the other element, and configurations whereby anelement is indirectly secured to another element by affixing the elementto intermediate member(s) which in turn are affixed to the otherelement). Usually, the topsheet 24 and the backsheet 25 are joineddirectly to each other in some locations (e.g. on or close to theperiphery of the article) and are indirectly joined together in otherlocations by directly joining them to one or more other elements of thearticle 20.

The topsheet 24 is preferably compliant, soft-feeling, andnon-irritating to the wearer's skin. Further, at least a portion of thetopsheet 24 is liquid permeable, permitting liquids to readily penetratethrough its thickness. A suitable topsheet may be manufactured from awide range of materials, such as porous foams, reticulated foams,apertured plastic films, or woven or nonwoven materials of naturalfibers (e.g., wood or cotton fibers), synthetic fibers or filaments(e.g., polyester or polypropylene or bicomponent PE/PP fibers ormixtures thereof), or a combination of natural and synthetic fibers. Ifthe topsheet 24 includes fibers, the fibers may be spunbond, carded,wet-laid, meltblown, hydroentangled, or otherwise processed as is knownin the art, in particular spunbond PP nonwoven. A suitable topsheetcomprising a web of staple-length polypropylene fibers is manufacturedby Veratec, Inc., a Division of International Paper Company, of Walpole,Mass. under the designation P-8.

Suitable formed film topsheets are also described in U.S. Pat. No.3,929,135, U.S. Pat. No. 4,324,246, U.S. Pat. No. 4,342,314, U.S. Pat.No. 4,463,045, and U.S. Pat. No. 5,006,394. Other suitable topsheets maybe made in accordance with U.S. Pat. No. 4,609,518 and U.S. Pat. No.4,629,643. Such formed films are available from The Procter & GambleCompany of Cincinnati, Ohio as “DRI-WEAVE” and from TredegarCorporation, based in Richmond, Va., as “CLIFF-T”.

Any portion of the topsheet may be coated with a lotion as is known inthe art. Examples of suitable lotions include those described in U.S.Pat. No. 5,607,760, U.S. Pat. No. 5,609,587, U.S. Pat. No. 5,643,588,U.S. Pat. No. 5,968,025 and U.S. Pat. No. 6,716,441. The topsheet 24 mayalso include or be treated with antibacterial agents, some examples ofwhich are disclosed in WO 95/24173. Further, the topsheet, the backsheetor any portion of the topsheet or backsheet may be embossed and/or mattefinished to provide a more cloth like appearance.

The topsheet 24 may comprise one or more apertures to ease penetrationof exudates therethrough, such as urine and/or feces (solid, semi-solid,or liquid). The size of at least the primary aperture is important inachieving the desired waste encapsulation performance. If the primaryaperture is too small, the waste may not pass through the aperture,either due to poor alignment of the waste source and the aperturelocation or due to fecal masses having a diameter greater than theaperture. If the aperture is too large, the area of skin that may becontaminated by “rewet” from the article is increased. Typically, thetotal area of the apertures at the surface of a diaper may have an areaof between about 10 cm² and about 50 cm², in particular between about 15cm² and 35 cm². Examples of apertured topsheet are disclosed in U.S.Pat. No. 6,632,504. WO 2011/163582 also discloses suitable coloredtopsheet having a basis weight of from 12 to 18 gsm and comprising aplurality of bonded points. Each of the bonded points has a surface areaof from 2 mm² to 5 mm² and the cumulated surface area of the pluralityof bonded points is from 10 to 25% of the total surface area of thetopsheet.

Typical diaper topsheets have a basis weight of from about 10 to about28 gsm, in particular between from about 12 to about 18 gsm but otherbasis weights are possible.

Backsheet 25

The backsheet 25 is generally that portion of the absorbent article 20which forms the majority of the external surface of the article whenworn by the user. The backsheet 25 is positioned towards the bottom side290 of the absorbent core 28 and prevents the exudates absorbed andcontained therein from soiling articles such as bed sheets andundergarments. The backsheet 25 is typically impermeable to liquids(e.g. urine). The backsheet 25 may for example be or comprise a thinplastic film such as a thermoplastic film having a thickness of about0.012 mm to about 0.051 mm. Exemplary backsheet films include thosemanufactured by Tredegar Corporation, based in Richmond, Va., and soldunder the trade name CPC2 film. Other suitable backsheet materials mayinclude breathable materials which permit vapors to escape from thearticle 20 while still preventing exudates from passing through thebacksheet 25. Exemplary breathable materials may include materials suchas woven webs, nonwoven webs, composite materials such as film-coatednonwoven webs, microporous films such as manufactured by Mitsui ToatsuCo., of Japan under the designation ESPOIR NO and by TredegarCorporation of Richmond, Va., and sold under the designation EXAIRE, andmonolithic films such as manufactured by Clopay Corporation, Cincinnati,Ohio under the name HYTREL blend P18-3097. Some breathable compositematerials are described in greater detail in WO 95/16746 (E. I. DuPont),U.S. Pat. No. 5,938,648 (LaVon et al.), U.S. Pat. No. 4,681,793 (Linmanet al.), U.S. Pat. No. 5,865,823 (Curro), U.S. Pat. No. 5,571,096(Dobrin et al.) and U.S. Pat. No. 6,946,585 (London Brown).

The backsheet 25 may be joined to the topsheet 24, the absorbent core 28or any other element of the diaper 20 by any attachment means known inthe art. Suitable attachment means are described above with respect tomeans for joining the topsheet 24 to other elements of the article 20.For example, the attachment means may include a uniform continuous layerof adhesive, a patterned layer of adhesive, or an array of separatelines, spirals, or spots of adhesive. Suitable attachment meanscomprises an open pattern network of filaments of adhesive as disclosedin U.S. Pat. No. 4,573,986. Other suitable attachment means includeseveral lines of adhesive filaments which are swirled into a spiralpattern, as is illustrated by the apparatus and methods shown in U.S.Pat. No. 3,911,173, U.S. Pat. No. 4,785,996; and U.S. Pat. No.4,842,666. Adhesives which have been found to be satisfactory aremanufactured by H. B. Fuller Company of St. Paul, Minn. and marketed asHL-1620 and HL 1358-XZP. Alternatively, the attachment means maycomprise heat bonds, pressure bonds, ultrasonic bonds, dynamicmechanical bonds, or any other suitable attachment means or combinationsof these attachment means as are known in the art.

Acquisition-Distribution System 54

The absorbent articles of the invention may comprise an acquisitionlayer, a distribution layer, or combination of both (herein collectivelyreferred to as acquisition-distribution system “ADS”). The function ofthe ADS is typically to quickly acquire the fluid and distribute it tothe absorbent core in an efficient manner. The ADS may comprise one, twoor more layers, which may form a unitary layer or remain discrete layerswhich may be attached to each other. The ADS may in particular comprisestwo layers: a distribution layer and an acquisition layer disposedbetween the absorbent core and the topsheet, but the invention is notrestricted to this example. Typically, the ADS will not comprise SAP asthis may slow the acquisition and distribution of the fluid. The priorart discloses many type of acquisition-distribution system, see forexample WO 2000/59430 (Daley), WO 95/10996 (Richards), U.S. Pat. No.5,700,254 (McDowall), WO 02/067809 (Graef). The ADS may, although notnecessarily, comprise two layers: a distribution layer and anacquisition layer, which will now be exemplified in more detail.

Distribution Layer

The function of a distribution layer is to spread the insulting fluidliquid over a larger surface within the article so that the absorbentcapacity of the core can be more efficiently used. Typically thedistribution layer is made of a nonwoven material based on synthetic orcellulosic fibers and having a relatively low density. The density ofthe distribution layer may vary depending on the compression of thearticle, but may typically range from 0.03 to 0.25 g/cm³, in particularfrom 0.05 to 0.15 g/cm³ measured at 0.30 psi (2.07 kPa). Thedistribution layer 54 may also be a material having a water retentionvalue of from 25 to 60, preferably from 30 to 45, measured as indicatedin the procedure disclosed in U.S. Pat. No. 5,137,537. The distributionlayer 54 may typically have an average basis weight of from 30 to 400g/m², in particular from 100 to 300 g/m².

The distribution layer may for example comprise at least 50% by weightof crosslinked cellulose fibers. The crosslinked cellulosic fibers maybe crimped, twisted, or curled, or a combination thereof includingcrimped, twisted, and curled. This type of material has been used in thepast in disposable diapers as part of an acquisition system, for exampleUS 2008/0312622 A1 (Hundorf). The crosslinked cellulosic fibers providehigher resilience and therefore higher resistance against thecompression in the product packaging or in use conditions, e.g. underbaby weight.

Exemplary chemically crosslinked cellulosic fibers suitable for adistribution layer are disclosed in U.S. Pat. No. 5,549,791, U.S. Pat.No. 5,137,537, WO 95/34329 or US 2007/118087. Exemplary crosslinkingagents include polycarboxylic acids such as citric acid and/orpolyacrylic acids such as acrylic acid and maleic acid copolymers. Forexample, the crosslinked cellulosic fibers may have between about 0.5mole % and about 10.0 mole % of a C2-C9 polycarboxylic acid crosslinkingagent, calculated on a cellulose anhydroglucose molar basis, reactedwith said fibers in an intrafiber ester crosslink bond form. The C2-C9polycarboxylic acid crosslinking agent may be selected from the groupconsisting of:

-   -   aliphatic and alicyclic C2-C9 polycarboxylic acids having at        least three carboxyl groups per molecule; and    -   aliphatic and alicyclic C2-C9 polycarboxylic acids having two        carboxyl groups per molecule and having a carbon-carbon double        bond located alpha, beta to one or both of the carboxyl groups,        wherein one carboxyl group in said C2-C9 polycarboxylic acid        crosslinking agent is separated from a second carboxyl group by        either two or three carbon atoms. The fibers may have in        particular between about 1.5 mole % and about 6.0 mole %        crosslinking agent, calculated on a cellulose anhydroglucose        molar basis, reacted therewith in the form of intrafiber ester        crosslink bonds. The crosslinking agent may be selected from the        group consisting of citric acid, 1, 2, 3, 4 butane        tetracarboxylic acid, and 1, 2, 3 propane tricarboxylic acid, in        particular citric acid.

Polyacrylic acid crosslinking agents may also be selected frompolyacrylic acid homopolymers, copolymers of acrylic acid, and mixturesthereof. The fibers may have between 1.0 weight % and 10.0 weight %,preferably between 3 weight % and 7 weight %, of these crosslinkingagents, calculated on a dry fiber weight basis, reacted therewith in theform of intra-fiber crosslink bonds. The crosslinking agent may be apolyacrylic acid polymer having a molecular weight of from 500 to40,000, preferably from 1,000 to 20,000. The polymeric polyacrylic acidcrosslinking agent may be a copolymer of acrylic acid and maleic acid,in particular wherein the weight ratio of acrylic acid to maleic acid isfrom 10:1 to 1:1, preferably from 5:1 to 1.5:1. An effective amount ofcitric acid may be further mixed with said polymeric polyacrylic acidcrosslinking agent.

The distribution layer comprising crosslinked cellulose fibers maycomprise other fibers, but this layer may advantageously comprise atleast 50%, or 60%, or 70%, or 80%, or 90% or even up to 100%, by weightof the layer, of crosslinked cellulose fibers (including thecrosslinking agents). Examples of such mixed layer of crosslinkedcellulose fibers may comprise about 70% by weight of chemicallycrosslinked cellulose fibers, about 10% by weight polyester (PET)fibers, and about 20% by weight untreated pulp fibers. In anotherexample, the layer of crosslinked cellulose fibers may comprise about70% by weight chemically crosslinked cellulose fibers, about 20% byweight lyocell fibers, and about 10% by weight PET fibers. In anotherexample, the layer may comprise about 68% by weight chemicallycrosslinked cellulose fibers, about 16% by weight untreated pulp fibers,and about 16% by weight PET fibers. In another example, the layer ofcrosslinked cellulose fibers may comprise from about 90-100% by weightchemically crosslinked cellulose fibers.

Acquisition Layer

The absorbent article 20 may comprise an acquisition layer 52, whosefunction is to quickly acquire the fluid away from the topsheet so as toprovide a good dryness for the wearer. The acquisition layer istypically placed directly under the topsheet. If present, thedistribution layer may be at least partially disposed under theacquisition layer. The acquisition layer may typically be or comprise anon-woven material, for example a SMS or SMMS material, comprising aspunbonded, a melt-blown and a further spunbonded layer or alternativelya carded chemical-bonded nonwoven. The non-woven material may inparticular be latex bonded. Exemplary upper acquisition layers 52 aredisclosed in U.S. Pat. No. 7,786,341. Carded, resin-bonded nonwovens maybe used, in particular where the fibers used are solid round or roundand hollow PET staple fibers (50/50 or 40/60 mix of 6 denier and 9denier fibers). An exemplary binder is a butadiene/styrene latex.Nonwovens have the advantage that they can be manufactured outside theconverting line and stored and used as a roll of material. Furtheruseful nonwovens are described in U.S. Pat. No. 6,645,569 (Cramer etal.), U.S. Pat. No. 6,863,933 (Cramer et al.), U.S. Pat. No. 7,112,621(Rohrbaugh et al.), US 2003/148684 (Cramer et al.) and US 2005/008839(Cramer et al.).

The acquisition layer may be stabilized by a latex binder, for example astyrene-butadiene latex binder (SB latex). Processes for obtaining suchlatices are known, for example, from EP 149880 (Kwok) and US2003/0105190 (Diehl et al.). In certain embodiments, the binder may bepresent in the acquisition layer 52 in excess of about 12%, about 14% orabout 16% by weight. SB latex is available under the trade name GENFLO™3160 (OMNOVA Solutions Inc.; Akron, Ohio).

A further acquisition layer (not shown) may be used in addition to thefirst acquisition layer described above. For example a tissue layer maybe placed between the first acquisition layer and the distributionlayer. The tissue may have enhanced capillarity distribution propertiescompared to the acquisition layer described above. The tissue and thefirst acquisition layer may be of the same size or may be of differentsize, for example the tissue layer may extend further in the back of theabsorbent article than the first acquisition layer. An example of ahydrophilic tissue is a 13 to 15 gsm high wet strength tissue made ofcellulose fibers from supplier Havix.

Fastening System 42, 44

The absorbent article may include a fastening system. The fasteningsystem can be used to provide lateral tensions about the circumferenceof the absorbent article to hold the absorbent article on the wearer.This fastening system is not necessary for training pant article sincethe waist region of these articles is already bonded. The fasteningsystem usually comprises a fastener 42 such as tape tabs, hook and loopfastening components, interlocking fasteners such as tabs & slots,buckles, buttons, snaps, and/or hermaphroditic fastening components,although any other known fastening means are generally acceptable. Alanding zone 44 is normally provided on the front waist region of thearticle for the fastener 42 to be releasably attached. Some exemplarysurface fastening systems are disclosed in U.S. Pat. No. 3,848,594, U.S.Pat. No. 4,662,875, U.S. Pat. No. 4,846,815, U.S. Pat. No. 4,894,060,U.S. Pat. No. 4,946,527, U.S. Pat. No. 5,151,092 and U.S. Pat. No.5,221,274 (Buell). An exemplary interlocking fastening system isdisclosed in U.S. Pat. No. 6,432,098. The fastening system may alsoprovide a means for holding the article in a disposal configuration asdisclosed in U.S. Pat. No. 4,963,140 (Robertson et al.)

The fastening system may also include primary and secondary fasteningsystems, as disclosed in U.S. Pat. No. 4,699,622 to reduce shifting ofoverlapped portions or to improve fit as disclosed in U.S. Pat. No.5,242,436, U.S. Pat. No. 5,499,978, U.S. Pat. No. 5,507,736, and U.S.Pat. No. 5,591,152.

Front and Back Ears 46, 40

The absorbent article may comprise front ears 46 and back ears 40 as isknown in the art. The ears can be integral part of the chassis, forexample formed from the topsheet and/or backsheet as side panel.Alternatively, as represented in FIG. 8, they may be separate elementsattached by gluing and/or heat embossing. The back ears 40 areadvantageously stretchable to facilitate the attachment of the tabs 42on the landing zone 44 and maintain the taped diapers in place aroundthe wearer's waist. The front ears 46 may also be elastic or extensibleto provide a more comfortable and contouring fit by initiallyconformably fitting the absorbent article to the wearer and sustainingthis fit throughout the time of wear well past when absorbent articlehas been loaded with exudates since the elasticized ears allow the sidesof the absorbent article to expand and contract.

Barrier Leg Cuffs 34 and Gasketing Cuffs 32

Absorbent articles such as diapers or training pants may typicallyfurther comprise components that improve the fit of the article aroundthe legs of the wearer, in particular barrier leg cuffs 34 and gasketingcuffs 32. The barrier leg cuffs 32 may be formed by a piece of material,typically a nonwoven, which is partially bonded to the rest of thearticle and can be partially raised away and thus stand up from theplane defined by the topsheet, when the article is pulled flat as shownfor example in FIGS. 1 and 2. The barrier leg cuffs 34 can provideimproved containment of liquids and other body exudates approximately atthe junction of the torso and legs of the wearer. The barrier leg cuffs34 extend at least partially between the front edge and the back edge ofthe absorbent article on opposite sides of the longitudinal axis and areat least present adjacent to the crotch point (C).

The barrier leg cuffs 34 may be delimited by a proximal edge 64 joinedto the rest of the article, typically the topsheet and/or the backsheet,and a free terminal edge 66 intended to contact and form a seal with thewearer's skin. The barrier leg cuffs 34 may be joined at the proximaledge 64 with the chassis of the article by a bond 65 which may be madefor example by adhesive bonding, fusion bonding or combination of knownbonding means. The bond 65 at the proximal edge 64 may be continuous orintermittent.

The barrier leg cuffs 34 can be integral with (i.e. formed from) thetopsheet or the backsheet, or more typically be formed from a separatematerial joined to the rest of the article. Typically the material ofthe barrier leg cuffs may extend through the whole length of the articlebut is “tack bonded” to the topsheet towards the front edge and backedge of the article so that in these sections the barrier leg cuffmaterial remains flush with the topsheet. Each barrier leg cuff 34 maycomprise one, two or more elastic strings 35 close to this free terminaledge 66 to provide a better seal.

In addition to the barrier leg cuffs 34, the article may comprisegasketing cuffs 32, which are formed in the same plane as the chassis ofabsorbent article, in particular may be at least partially enclosedbetween the topsheet and the backsheet, and may be placed laterallyoutwardly relative to the barrier leg cuffs 34. The gasketing cuffs 32can provide a better seal around the thighs of the wearer. Usually eachgasketing leg cuff 32 will comprise one or more elastic string orelastic element 33 comprised in the chassis of the diaper for examplebetween the topsheet and backsheet in the area of the leg openings.

U.S. Pat. No. 3,860,003 describes a disposable diaper which provides acontractible leg opening having a side flap and one or more elasticmembers to provide an elasticized leg cuff (a gasketing cuff). U.S. Pat.No. 4,808,178 (Aziz) and U.S. Pat. No. 4,909,803 (Aziz) describedisposable diapers having “stand-up” elasticized flaps (barrier legcuffs) which improve the containment of the leg regions. U.S. Pat. No.4,695,278 (Lawson) and U.S. Pat. No. 4,795,454 (Dragoo) describedisposable diapers having dual cuffs, including gasketing cuffs andbarrier leg cuffs. All or a portion of the barrier leg and/or gasketingcuffs may be treated with a lotion.

Elastic Waist Feature

The absorbent article may also comprise at least one elastic waistfeature (not represented) that helps to provide improved fit andcontainment. The elastic waist feature is generally intended toelastically expand and contract to dynamically fit the wearer's waist.The elastic waist feature preferably extends at least longitudinallyoutwardly from at least one waist edge of the absorbent core 28 andgenerally forms at least a portion of the back side of the absorbentarticle. Disposable diapers can be constructed so as to have two elasticwaist features, one positioned in the front waist region and onepositioned in the back waist region. The elastic waist feature may beconstructed in a number of different configurations including thosedescribed in U.S. Pat. No. 4,515,595, U.S. Pat. No. 4,710,189, U.S. Pat.No. 5,151,092 and U.S. Pat. No. 5,221,274.

Relations Between the Layers and Components

Typically, adjacent layers will be joined together using conventionalbonding method such as adhesive coating via slot coating or spraying onthe whole or part of the surface of the layer, or thermo-bonding, orpressure bonding or combinations thereof. Most of the bonding betweencomponents is for clarity and readability not represented in the Figure.Bonding between the layers of the article should be considered to bepresent unless specifically excluded. Adhesives may be typically used toimprove the adhesion of the different layers, for example between thebacksheet and the core wrap. The adhesives used may be any standardhotmelt glue as known in the art.

Method of Making

The absorbent article of the invention may be made by any conventionalmethods known in the art. In particular the articles may be hand-made orindustrially produced at high speed on a modern converting line. Theabsorbent core of the invention can in particular be made industriallyby combining two absorbent structures 70 and 70′ using the methodgenerally disclosed in WO2008/155699 with some adaptations. Such amethod is schematically disclosed in FIG. 11.

A first printing unit 134 for making an absorbent structure having thelayers corresponding to the structure shown on FIG. 5 is illustrated onthe left side of FIG. 11. The first printing unit 134 comprise anauxiliary glue applicator 148 for applying the auxiliary glue 72 to thesubstrate 16, a first rotatable support roll 152 for receiving the firstsubstrate 16, a first hopper 154 for holding and dispensing an absorbentparticulate polymer material, a first printing roll 156 for depositingthe absorbent particulate polymer layer 61 comprising material landareas and junction areas from the hopper 154 to a deposition area 73 onthe substrate 16, and a first thermoplastic adhesive material applicator158 for applying the fibrous thermoplastic adhesive material 74. Theauxiliary glue applicator 148 may be a nozzle system which can provide arelatively thin but wide curtain of thermoplastic adhesive material assuggested in WO2008/155699, but may also alternatively andadvantageously comprise a slot coater for applying simultaneouslyseveral slots 72 s of auxiliary glue 72 longitudinally along a desiredwidth of the substrate, which may correspond to the width of theabsorbent material deposition area 73 or be shorter or if wished larger.The auxiliary glue applicator may be fitted with a manifold whichintermittently stops the delivery of the auxiliary glue so that therethe auxiliary layer is only applied in the desired auxiliary glueapplication area 71. The SAP printing roll 156 and fibrous layeradhesive applicator 158 may be as further detailed in WO2008/155699.

The absorbent structure 70 obtained by the printing unit 134 may bedirectly put in face to face relation with a second substrate 16′, ormay be combined with a second absorbent structure 70′, to form anabsorbent core comprising two absorbent layers 61, 62 as shown in FIG.3. This second absorbent structure 70′ may then be formed on the secondprinting unit 132 as shown on the right side of FIG. 11, which may begenerally identical to the first printing unit 134. The second printingunit 132 may comprise a second auxiliary glue applicator 136 which maybe a slot coater for optionally applying a second auxiliary glue 72′ tothe substrate 16′, a second rotatable support roll 140 for receiving thesubstrate 16′, a second hopper 142 for holding absorbent particulatepolymer material, a second printing roll 144 for transferring theabsorbent particulate polymer material to the substrate 16′, and athermoplastic adhesive material applicator 146 for applying athermoplastic fibrous adhesive material 74′ to the substrate 16′ and theabsorbent particulate polymer layer 62 thereon.

The absorbent structures may be combined by applying pressure in the nip162 between the two support rolls 140, 152. The lateral seals are formedas a C-wrap in the seal forming guide roller 160 by continuously foldingthe laterally extending flaps of one of the substrate. The absorbentcores 28 can then be individualized by forming the front and back sealsand cutting the web of the core material at the required interval. Thecontinuous flow of absorbent cores can then be integrated into aconverting process for making an absorbent article.

Test Procedures

The values indicated herein are measured according to the methodsindicated herein below, unless specified otherwise. All measurements areperformed at 21° C.±2° C. and 50%±20% RH, unless specified otherwise.All samples should be kept at least 24 hours in these conditions toequilibrate before conducting the tests, unless indicated otherwise. Allmeasurements should be reproduced on at least 4 samples and the averagevalue obtained indicated, unless otherwise indicated.

Centrifuge Retention Capacity (CRC)

The CRC measures the liquid absorbed by the superabsorbent polymerparticles for free swelling in excess liquid. The CRC is measuredaccording to EDANA method WSP 241.2-05.

Dry Absorbent Core Caliper Test

This test may be used to measure the caliper of the absorbent core(before use i.e. without fluid loading) in a standardized manner.

Equipment: Mitutoyo manual caliper gauge with a resolution of 0.01 mm,or equivalent instrument.

Contact Foot: Flat circular foot with a diameter of 17.0 mm (±0.2 mm). Acircular weight may be applied to the foot (e.g., a weight with a slotto facilitate application around the instrument shaft) to achieve thetarget weight. The total weight of foot and added weight (includingshaft) is selected to provide 2.07 kPa (0.30 psi) of pressure to thesample.

The caliper gauge is mounted with the lower surface of the contact footin an horizontal plane so that the lower surface of the contact footcontacts the center of the flat horizontal upper surface of a base plateapproximately 20×25 cm. The gauge is set to read zero with the contactfoot resting on the base plate.

Ruler: Calibrated metal ruler graduated in mm.

Stopwatch: Accuracy 1 second.

Sample preparation: The core is conditioned at least 24 hours asindicated above.

Measurement procedure: The core is laid flat with the bottom side, i.e.the side intended to be placed towards the backsheet in the finishedarticle facing down. The point of measurement (e.g. the crotch point C)is carefully drawn on the top side of the core taking care not tocompress or deform the core.

The contact foot of the caliper gauge is raised and the core is placedflat on the base plate of the caliper gauge with the top side of thecore up so that when lowered, the center of the foot is on the markedmeasuring point.

The foot is gently lowered onto the article and released (ensurecalibration to “0” prior to the start of the measurement). The calipervalue is read to the nearest 0.01 mm, 10 seconds after the foot isreleased.

The procedure is repeated for each measuring point. If there is a foldat the measuring point, the measurement is done in the closest area tothis point but without any folds. Ten articles are measured in thismanner for a given product and the average caliper is calculated andreported with an accuracy of one tenth mm.

Absorbent Article Caliper Test

The Absorbent Article Caliper Test can be performed as for the DryAbsorbent Core Caliper Test with the difference that the caliper of thefinished absorbent article is measured instead of the caliper of thecore. The point of measurement may be the intersection of thelongitudinal axis 80′ and transversal axis 90′ of the absorbent article.If the absorbent articles were provided folded and/or in a package, thearticles to be measured are unfolded and/or removed from the center areaof the package. If the package contains more than 4 articles, the outermost two articles on each side of the package are not used in thetesting. If the package contains more than 4 but fewer than 14 articles,then more than one package of articles is required to complete thetesting. If the package contains 14 or more articles, then only onepackage of articles is required to perform the testing. If the packagecontains 4 or fewer articles then all articles in the package aremeasured and multiple packages are required to perform the measurement.Caliper readings should be taken 24±1 hours after the article is removedfrom the package, unfolded and conditioned. Physical manipulation ofproduct should be minimal and restricted only to necessary samplepreparation.

Any elastic components of the article that prevent the article frombeing laid flat under the caliper foot are cut or removed. These mayinclude leg cuffs or waistbands. Pant-type articles are opened or cutalong the side seams as necessary. Apply sufficient tension to flattenout any folds/wrinkles Care is taken to avoid touching and/orcompressing the area of measurement.

Example

An exemplary absorbent core according to the first aspect of theinvention and roughly corresponding to the schematic view shown in FIG.6 can be made as follows. The first substrate 16 is a 10 gsm SMSnonwoven substrate which has been surfactant treated to be hydrophilicand is 390 mm long and 165 mm wide. The second substrate is aninherently hydrophobic 10 gsm SMS nonwoven substrate 390 mm long and 130mm wide.

An auxiliary glue 72 (e.g. Fuller hot-melt adhesive 1286 or 1358) isapplied on the first substrate by slot coating in a pattern of 41 slots1 mm wide with a distance of 1 mm between the slots. The applicationarea thus has a constant width of about 81 mm. The application area iscentered on the longitudinal centerline of the first substrate. Theslots start at a distance of 57 mm from the front edge of the substrateand extend to a distance of 237 mm towards from the back edge of thesubstrate. The application area 71 of the auxiliary adhesive is thusrectangular and has a surface of about 19200 square mm, or 192 squarecm. The glue may be applied at a basis weight of about 8 gsm (grams persquare meter) in the slots. The total amount of auxiliary glue on thefirst substrate is about 80 mg.

A superabsorbent polymer 60 in particulate form is then applied on thefirst substrate in a regular pattern of rectangular land areas 75oriented in the transversal direction of the substrate as schematicallyshown on FIG. 5, each area being about 10 mm wide and 110 mm long. Thefirst land area started at a distance of 15 mm from the front edge ofthe substrate. The junction areas 76 that separate each land area areabout 1-2 mm wide. The last land area is placed at a distance of 15 mmfrom the back edge of the substrate, thus providing the substrate withabout thirty SAP land areas. The amount of SAP in each land areas variesso as to provide a profiled repartition of the absorbent material. Theabsorbent material was deposited at a higher basis weight in crotchregion of the core, and at lower basis weight towards the back region ofthe core and at an intermediate value towards the front of the core. Twolongitudinally extending absorbent material free areas with a concaveoutline towards the centerline as illustrated on FIG. 5 are alsoprovided. The absorbent material free areas are thus fully encompassedwithin the auxiliary glue application area. The length L′ of thesematerial free areas 26 a,b as projected on the longitudinal axis isabout 230 mm.

A fibrous thermoplastic layer 74 (e.g. NW1151ZP hot-melt adhesive exFuller) may be generally uniformly sprayed at a basis weight of 5 gsm tocover the absorbent material land areas deposited on the first substrateand junction areas in between, stopping for example at 5 mm from eachlateral sides of the substrate (as illustrated in FIG. 5).

This first absorbent structure 70 as described above is combined with asecond absorbent structure comprising the second substrate 16′ andanother layer of absorbent material 62 having generally the samerepartition of land areas 75′ and junction areas 76′, absorbent materialfree areas 26 a,b and fibrous adhesive 74′. The second substrate may ormay not comprise a second auxiliary adhesive layer. The two substratesare combined so that the land areas have a slight offset of e.g. ca. 5mm in the longitudinal direction so that land areas of one structure arecover the junction areas of the other structure. The material free areas26 a,b on both absorbent structures are registered so that the combinedabsorbent core comprises two channel-forming areas 26 a,b similar tothose represented in FIG. 6. The two substrates are attached throughthese areas 26 a,b by the auxiliary glue 72 and to a lesser extent thefibrous adhesive. This allows forming a combined substantiallycontinuous absorbent material area within the core wrap. The combinedabsorbent material deposition area 73 is thus rectangular with a widthof 110 mm and a length of about 360 mm and substantially continuous. Thesurface of the absorbent material deposition area in this example isthus 39,600 square mm, or 396 square cm. The auxiliary glue applicationarea 71 is thus about 51.5% smaller than the absorbent materialdeposition area 73 (=(396−192)/396). The total amount of SAP in the coremay be about 13.5 g equally deposited on the first and the secondsubstrate.

The first substrate being wider (165 mm) than the second substrate, thelaterally extending flaps from the first substrate can be folded aroundthe side edges 284, 286 of the core onto the external surface of thesecond substrate to form a C-wrap along the length of the lateral edgesof the core. The upper substrate 16 is thus C-wrapped around the lowersubstrate 16′ along the lateral side edges of the core. The lateraledges of the lower substrate 16′ can be slightly formed upwards on theedge of the absorbent material of the core as shown on FIG. 2 so thatthe overall width of the folded core wrap is about 120 mm. Each C-wrapseals may e.g. comprise a glue applied as 2 slots each at 20 gsm, eachslot having a slot width of 3 mm and a slot length of 390 mm. The frontend and back end of the substrates can be glued in face to face relationto form two longitudinal sandwich seal 280′, 282′, for example using aseries of longitudinal glue slots across the width of the core asillustrated on FIG. 1.

The absorbent core can be integrated in an absorbent article such asdiaper chassis as illustrated on FIG. 8. When the absorbent core absorbsa fluid, the absorbent material 60 starts swelling and the bonded areas26 within the absorbent material deposition area start forming channels26′, as illustrated on FIG. 10. At higher amount of liquid saturation,these core wrap bonds 27 may start opening to provide more volume forthe absorbent material to swell. The C-wrap seal along each longitudinaledges of the core may remain permanent through the swelling of theabsorbent material and until full saturation of the core. The absorbentcore has good wet and dry SAP immobilization properties as well asreduced usage of glue.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application and any patent application or patent to which thisapplication claims priority or benefit thereof, is hereby incorporatedherein by reference in its entirety unless expressly excluded orotherwise limited. The citation of any document is not an admission thatit is prior art with respect to any invention disclosed or claimedherein or that it alone, or in any combination with any other referenceor references, teaches, suggests or discloses any such invention.Further, to the extent that any meaning or definition of a term in thisdocument conflicts with any meaning or definition of the same term in adocument incorporated by reference, the meaning or definition assignedto that term in this document shall govern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A absorbent core extending in a transversaldirection and a longitudinal direction, the absorbent core having afront edge, a back edge and two longitudinally extending side edges, theabsorbent core comprising: (a) a core wrap comprising a first substrateand a second substrate wherein each substrate comprises an inner surfaceand an outer surface; (b) an absorbent material comprising from about80% to about 100%, by weight, of superabsorbent polymer, and having aperiphery defining an absorbent material deposition area, between thefirst substrate and the second substrate, the absorbent materialdeposition area encompassing one or more areas substantially free ofabsorbent material; and (c) an auxiliary glue applied directly to theinner surface of the first substrate and defining an auxiliary glueapplication area; wherein the auxiliary glue at least partially bondsthe inner surface of the first substrate to the inner surface of thesecond substrate through the one or more areas substantially free ofabsorbent material, so that when the absorbent material swells, the corewrap forms channels in the areas substantially free of absorbentmaterial; and wherein the auxiliary glue application area is smallerthan the absorbent material deposition area and the first substrateand/or the second substrate comprises at least one outwardly extendingflap which is folded around at least one of the front, back, or any ofthe side edges of the core, and the at least one flap is bonded to theexternal surface of the other substrate to form a C-wrap seal along theat least one edge of the absorbent core.
 2. The absorbent core of claim1, comprising two laterally extending flaps, each being folded aroundone of the longitudinally extending side edges of the core to form aC-wrap seal along each side edge of the absorbent core.
 3. The absorbentcore of claim 1, wherein the absorbent material is in particulate form.4. The absorbent core of claim 1, wherein the auxiliary glue applicationarea is at least about 20% smaller than the absorbent materialdeposition area.
 5. The absorbent core of claim 1, wherein the auxiliaryglue application area is from about 20% to about 80% smaller than theabsorbent material deposition area.
 6. The absorbent core of claim 1,wherein the auxiliary glue application area is shorter in thelongitudinal direction, or in the transversal direction, or in bothdirections, than the absorbent material deposition area.
 7. Theabsorbent core of claim 1, wherein the absorbent material depositionarea comprises at least two areas substantially free of absorbentmaterial, said areas extending in the longitudinal direction and havinga length which is from about 10% to about 80%, of the length of thecore, and at least about 2 cm, as measured by projection on thelongitudinal axis.
 8. The absorbent core of claim 1, wherein theauxiliary glue application area comprises a series of glue slotsorientated along the longitudinal direction of the core and spacesbetween the slots.
 9. The absorbent core of claim 1, wherein theabsorbent material forms a substantially continuous layer of absorbentmaterial.
 10. The absorbent core of claim 1, wherein the absorbentmaterial is profiled at least in the longitudinal direction, so that theaverage basis weight of the absorbent material varies along thelongitudinal axis.
 11. The absorbent core of claim 10, wherein theabsorbent material is applied at a higher basis weight at the frontand/or center of the absorbent material deposition area, than at theback of the absorbent material deposition area.
 12. The absorbent coreof claim 1, wherein the auxiliary glue application area comprises asingle area encompassing the one or more areas substantially free ofabsorbent material.
 13. The absorbent core of claim 1, wherein theauxiliary glue application area comprises two or more sub-areas eachencompassing one or more of the areas substantially free of absorbentmaterial.
 14. The absorbent core of claim 1, wherein the absorbentmaterial comprises a first absorbent material layer deposited on thefirst substrate in a pattern having first absorbent material land areasand absorbent material-free junction areas.
 15. The absorbent core ofclaim 14, comprising at least one fibrous glue layer covering theabsorbent material land areas and absorbent material-free junction areasto further immobilize the first absorbent material layer.
 16. Theabsorbent core of claim 14, wherein the absorbent material furthercomprises a second absorbent material layer applied on the secondsubstrate in a pattern having second absorbent material land areas andabsorbent material-free junction areas, wherein the first and secondabsorbent material layers are combined to provide a substantiallycontinuous layer of absorbent material.
 17. The absorbent core of claim16, further comprising a second fibrous glue layer covering theabsorbent material land areas and absorbent material-free junction areasof the second absorbent material layer.
 18. The absorbent core of claim17, further comprising a second auxiliary glue applied directly to theinner surface of the second substrate and defining a second auxiliaryglue application area.
 19. An absorbent article comprising a topsheet, abacksheet, and an absorbent core according to claim
 1. 20. The absorbentarticle of claim 19, wherein the absorbent core is interposed betweenthe topsheet and the backsheet, and the first substrate being on thetopsheet-facing side of the core, and the second substrate being on thebacksheet-facing side of the core, and the first substrate comprises twolaterally, outwardly extending flaps that are folded around thelongitudinally extending side edges of the core and form a C-wrap sealalong each of these sides with the second substrate.